Sediment Profiling Photography 



Contrary to the other biological tests, this method was applied at sites throughout the 

 estuary. A sediment profiling camera was used to determine a variety of sedimentological 

 and biological properties of surficial sediments at 69 sites. The objective of this analysis was 

 not to evaluate the sensitivity of the test to a range in chemical contamination. Rather, it 

 was to characterize sediment properties, mainly indicative of organic enrichment, throughout 

 the San Francisco Bay estuary. However, 4 of the 69 sampling sites corresponded with those 

 sampled for toxicity testing, chemical analyses, and benthos. Therefore, the data from these 

 four sites are included in this report to facilitate a complete review of all the analyses 

 performed in San Francisco Bay. Details of methods and results for all 69 sites are presented 

 by Revelas et al. (1987). 



Data acquisition. Field operations were conducted by SAIC with the vessel PROPHECY 

 from 3 through 9 February, 1987. The environments surveyed included shallow fine-grained 

 areas, deep fine- and coarse-grained high energy channel habitats, active and inactive 

 disposal sites, creeks and river mouths, and ports and inner harbors. Five replicate 

 photographs were taken per site. 



Navigation and data logging,. Navigational control of the survey vessel during this project 

 was provided by the SAIC Integrated Navigation and Data Acquisition System (INDAS). 

 This particular system consisted of a Northstar 6000 LORAN-C receiver interfaced to a 

 Hewlett-Packard Series 200 model 20 microcomputer. A calibration procedure was utilized 

 during this project which resulted in a much more accurate LORAN-C positioning system than 

 is usually possible. In order to calibrate LORAN-C, it was necessary to position the LORAN- 

 C receiver at locations whose positions were known with a high degree of certainty. With 

 the resulting calibration factors applied to the incoming LORAN-C coordinates, the ship's 

 geodetic position was calculated to an accuracy of ± 20 meters. 



REMOTS™ images. REMOTS™ sediment-profile images were taken using a modified 

 Benthos Model 3731 Sediment-Profile camera (Benthos Inc. North Falmouth, Massachusetts). 

 The camera consisted of a wedge-shaped prism with a Plexiglas™ face plate; light was 

 provided by an internal strobe. The back of the prism had a mirror mounted at a 45-degree 

 angle to reflect the profile of the sediment-water interface up to the camera, which was 

 mounted horizontally on the top of the prism. The prism was filled with distilled water, 

 and because the object to be photographed was directly against the face plate, turbidity of 

 the ambient seawater was never a limiting factor. The camera was mounted on a large tube 

 frame and raised and lowered by winch. 



REMOTS™ image analyses. REMOTS™ measurements of all physical parameters and 

 some biological parameters were measured directly from the film negatives using a video 

 digitizer and computer image analysis system. Negatives were used for analysis instead of 

 positive prints in order to avoid changes in image density that can accompany the printing 

 of a positive image. Proprietary SAIC software allowed the measurement and storage of 

 data on 22 different variables for each REMOTS™ image obtained. 



Apparent redox potential discontinuity depth. Oxic near-surface marine sediments have a 

 higher reflectance value relative to underlying hypoxic or anoxic sediments. This 

 discontinuity is readily apparent in REMOTS™ images and is due to the fact that oxidized 

 surface sediment contains particles coated with ferric hydroxide (an olive color when 

 associated with particles), while the sulphidic sediments below this oxygenated layer are 

 gray to black. The boundary between the colored ferric hydroxide surface sediment and 

 underlying gray to black sediment is called the apparent redox potential discontinuity 

 (RPD) and its apparent depth was determined at each site. 



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